PARTIAL CHARACTERIZATION OF A NOVEL CARDIOINHIBITORY PEPTIDE FROM THEBRAIN OF THE SNAIL HELIX-ASPERSA

1. We report the isolation of a peptide from the brain of the snail He lix aspersa by radioimmunoassay using an antisomatostatin. 2. The sequ encing of an immunopositive fraction showed the presence of a new trid ecapeptide, termed Helix cardioinhibitory peptide (HCIP), with the fol lowing primary structure: e-Gln-Asn-Gln-Phe-Lys-Gly-lle-Gln-Gly-Arg-Ph e-NH2. It is structurally related to the Achatina cardioexcitatory pep tide (ACEP-1) and the terminal-amino acid sequence of HCIP is identica l to that of FMRFamide family peptides. 3. The synthetic HCIP was test ed on heart and neuronal activities and it was found to have inhibitor y actions not only on the ventricle but also on visceral neurons of th e central nervous system of Helix. Immunocytochemical investigation in dicates its presence in visceral and parietal ganglia, in which cells taking part in the regulation of the heartbeat have been previously id entified.